Keeping your body stable is helpful for paddling, and the important role of kicking is to keep your body stable.

There are many muscles on the foot, which is not suitable for long-term tendon-breaking action. So except for breaststroke and butterfly stroke, the thrust generated by kicking is very small. The ratio of thrust to speed generated by kicking is 2/5 in short-distance swimming and 1/5 in long-distance swimming. However, intensive kicking can make the body float and assist the arm in paddling. It's also important to kick harder when you are near the finish line.